The long term objectives of this project are to improve the imaging and economic performance of positron cameras (PET) so that their capability to image organ function and chemistry can be more widely applied. The detection system of a PET dictates its image quality and cost. This proposal aims at developing a new detector design concept for PET to serve these objectives. This project will (a) evaluate potential and unforeseen difficulties study basic characteristics: scintillation distribution and new techniques for controlling it, optical characteristics, inter-crystal Compton interaction cross-talk, and coincidence timing resolution, (b) develop prototype detectors using new light controlling techniques to achieve the ultimate spatial resolution possible and test the performance characteristics of the prototypes, and (c) develop a new count-rate enhancing circuit and integrate it into the prototype detection system to prevent/correct for detection signal pileup in high count-rate situations thus enhancing the count-rate capability of the proposed detector. This algorithm/circuit should also be usable in standard gamma and PET cameras to enhance their count rate capability, especially for high dose 0-15, Rb-82 and monoclonal antibody imaging. Two implementations of the detector concept will be investigated: (1) a high resolution. low cost implementation which may potentially decrease the $2,400,000 PET price to $1,400,000 while maintaining high resolution by using the same size detectors (6.5x6.5mm) as most current commercial PET, (2) a very high resolution implementation which significantly improves image resolution by decreasing the detector size from 6.5x6.5mm to 2.6x2.6mm, thus increasing the number of detectors by six times while potentially lowering the price of PET by 25%.